Imaging optical system for direct phase-angle measurement of radiation

Abstract

A method serves the direct phase-angle measurement of radiation, in particular of light radiation which is reflected from a body. The body is exposed to coherent radiation. The radiation reflected from the body is imaged by an imaging optical system (6) in an image plane in which a sensor is located. A reference radiation generated in accordance with the shearing method is superimposed on the sensor. The phase of the radiation from the body is determined from the measurement signals of the sensor. To improve such a method, the imaging optical system (6) possesses a diaphragm (11) having one or two apertures (12, 13) (FIG. 2a).

What is claimed is:  
     
       1. A method for a direct phase-angle measurement of radiation ( 2 ) passing through a body ( 3 ), comprising the steps of 
       exposing the body ( 3 ) to coherent radiation ( 2 ) of pre-determined frequency,  
       imaging radiation passing through the body ( 3 ) by an imaging optical system ( 6 ) in an image plane ( 7 ) in which a sensor ( 8 ) is located and possessing a diaphragm ( 11 ,  19 ) having at least one aperture ( 20 ),  
       positioning one of a wedge ( 14 ,  23 ), or folding wedges ( 16 ,  24 ) or two tilted parallel plates ( 17 ,  18 ,  25 ,  26 ) adjacent the diaphragm ( 11 ,  19 ),  
       positioning at least one lens element ( 9 ,  19 ) on a side of the wedge ( 14 ,  23 ), or folding wedges ( 16 ,  24 ) or tilted plates ( 17 ,  18 ,  25 ,  26 ) opposite said diaphragm ( 11 ,  19 ) or on a side of said diaphragm ( 11 ,  19 ) opposite the wedge ( 14 ,  23 ), or folding wedges ( 16 ,  24 ) or tilted parallel plates ( 17 ,  18 ,  25 ,  26 ),  
       superimposing a reference radiation which has been generated in accordance with a shearing method upon the sensor ( 8 ), and  
       determining phase of the radiation ( 5 ) from the body ( 3 ) by measurement signals of the sensor ( 8 ).  
     
     
       2. The method of  claim 1 , comprising the additional step of providing the diaphragm ( 19 ) with a single slit ( 20 ). 
     
     
       3. The method of  claim 1 , comprising the additional step of providing the diaphragm ( 11 ) with two slits ( 12 ,  13 ). 
     
     
       4. The method of  claim 2  comprising the additional step of adjusting breadth of the single slit ( 20 ) which is substantially rectangular. 
     
     
       5. The method of  claim 3 , comprising the additional step of providing the diaphragm ( 11 ) with two substantially rectangular slits ( 12 ,  13 ). 
     
     
       6. The method in accordance with  claim 5 , comprising the additional step of 
       adjusting at least one of distance (a) between said two slits ( 12 ,  13 ) and breadth (b) of each said slit ( 12 ,  13 ).  
     
     
       7. A method in accordance with  claim 6 , comprising the additional step of adjusting the imaging optical system ( 6 ) such that distance (a) between center lines of adjacent slits ( 12 ,  13 ) and breadth (b) of each said slit ( 12 ,  13 ) are equal. 
     
     
       8. The method in accordance with  claim 1 , comprising the additional step of providing a period of carrier frequency to cover multiple picture elements of the sensor ( 8 ). 
     
     
       9. The method in accordance with  claim 1 , comprising the step of generating a constant spatial carrier frequency. 
     
     
       10. A method for a direct phase-angle measurement of radiation ( 2 ) reflected by a body ( 3 ), comprising the steps of 
       coating the body ( 3 ) with lacquer in which particles diffusely reflecting the radiation are stored and then exposing the thus-coated body ( 3 ) to non-coherent radiation ( 2 ) of a pre-determined frequency,  
       imaging radiation reflected by the body ( 3 ) by an imaging optical system ( 6 ) in an image plane ( 7 ) in which a sensor ( 8 ) is located and possessing a diaphragm ( 19 ) having at least one aperture ( 20 ),  
       positioning one of a wedge ( 14 ,  23 ), or folding wedges ( 16 ,  24 ) or two tilted parallel plates ( 17 ,  18 ,  25 ,  26 ) adjacent the diaphragm ( 11 ,  19 ),  
       positioning at least one lens element ( 9 ,  19 ) on a side of the wedge ( 14 ,  23 ), or folding wedges ( 16 ,  24 ) or tilted plates ( 17 ,  18 ,  25 ,  26 ) opposite said diaphragm ( 11 ,  19 ) or on a side of said diaphragm ( 11 ,  19 ) opposite the wedge ( 14 ,  23 ), or folding wedges ( 16 ,  24 ) or tilted parallel plates ( 17 ,  18 ,  25 ,  26 ),  
       superimposing a reference radiation which has been generated in accordance with a shearing method upon the sensor ( 8 ), and  
       determining phase of the radiation ( 5 ) from the body ( 3 ) by measurement signals of the sensor ( 8 ).  
     
     
       11. The method of  claim 10 , comprising the additional step of providing the diaphragm ( 19 ) with a single slit ( 20 ). 
     
     
       12. The method of  claim 10 , comprising the additional step of providing the diaphragm ( 11 ) with two slits ( 12 ,  13 ). 
     
     
       13. The method of  claim 11 , comprising the additional step of adjusting breadth of the single slit ( 20 ) which is substantially rectangular. 
     
     
       14. The method of  claim 12 , comprising the additional step of providing the diaphragm ( 11 ) with two substantially rectangular slits ( 12 ,  13 ). 
     
     
       15. The method in accordance with  claim 14 , comprising the additional step of adjusting at least one of distance (a) between said two slits ( 12 ,  13 ) and breadth (b) of each said slit ( 12 ,  13 ). 
     
     
       16. A method in accordance with  claim 15 , comprising the additional step of adjusting the imaging optical system ( 6 ) such that distance (a) between center lines of adjacent slits ( 12 ,  13 ) and breadth (b) of each said slit ( 12 ,  13 ) are equal. 
     
     
       17. The method in accordance with  claim 10 , comprising the additional step of providing a period of carrier frequency to cover multiple picture elements of the sensor ( 8 ). 
     
     
       18. The method in accordance with  claim 10 , comprising the step of generating a constant spatial carrier frequency. 
     
     
       19. Apparatus for direct phase-angle measurement of radiation reflected from a body ( 3 ) or passing therethrough ( 3 ), comprising 
       a radiation source for emission of radiation ( 2 ) of certain frequency onto the body ( 3 ),  
       an imaging optical system ( 6 ) arranged for imaging radiation ( 5 ) reflected from the body ( 3 ) or passing therethrough ( 3 ), in an image plane ( 7 ) and possessing a diaphragm ( 11 ,  19 ) having at least one aperture ( 20 ),  
       a sensor ( 8 ) disposed in the image plane ( 7 ),  
       a wedge ( 14 ,  23 ), or folding wedges ( 16 ,  24 ) or two tilted parallel plates ( 17 ,  18 ,  25 ,  26 ) positioned adjacent to said diaphragm ( 11 ,  19 ) in said optical system ( 6 ),  
       at least one lens element ( 9 ,  19 ) positioned on a side of the wedge, or folding wedges ( 16 ,  24 ) or tilted parallel plates ( 17 ,  18 ,  25 ,  26 ) opposite from the diaphragm ( 11 ,  19 ) or on a side of the diaphragm ( 11 ,  19 ) opposite the wedge ( 14 ,  23 ), or folding wedges ( 16 ,  24 ) or tilted parallel plates ( 17 ,  18 ,  25 ,  26 ) and  
       a shearing optical system for generating a reference radiation in accordance with a shearing method.  
     
     
       20. An apparatus in accordance with  claim 19 , wherein the diaphragm ( 19 ) possesses a single substantially rectangular slit ( 20 ) having a breadth (b) which can be adjusted. 
     
     
       21. An apparatus in accordance with  claim 19 , wherein the diaphragm ( 11 ) possesses two substantially rectangular slits ( 12 ,  13 ). 
     
     
       22. An apparatus in accordance with  claim 21 , wherein distance (a) between the slits ( 12 ,  13 ) and breadth (b) of each said slit ( 12 ,  13 ) is adjustable. 
     
     
       23. An apparatus in accordance with  claim 22 , wherein the image optical system ( 6 ) is adjusted such that distance between center lines of adjacent rectangular slits ( 12 ,  13 ) equals breadth (b) of each said slit ( 12 ,  13 ). 
     
     
       24. An apparatus in accordance with  claim 19 , structured and arranged such that a period of a carrier frequency covers multiple picture elements of the sensor ( 8 ). 
     
     
       25. The apparatus in accordance with  claim 21 , wherein said diaphragm ( 11 ) comprises said rectangular slits ( 12 ,  13 ) laterally arranged adjacent to one another and comprising one of a 
       wedge ( 14 ) having an apex resting on a center line ( 15 ) situated between said two slits ( 12 ,  13 ),  
       a bi-prism ( 16 ) having an apex situated on a center line ( 15 ) between said two slits ( 12 ,  13 ), or  
       two tilted plates tilted ( 17 ,  18 ) outwardly from said diaphragm ( 11 ), being centered around a center line ( 15 ) situated between said two slits ( 12 ,  13 ) and having parallel incident and exit surfaces.  
     
     
       26. An apparatus in accordance with  claim 20 , wherein said diaphragm ( 19 ) comprises a single slit ( 20 ) and one of a 
       wedge ( 23 ) having a thickest base portion situated upon a center line of the slit ( 20 );  
       a bi-prism ( 24 ) situated to have an apex upon a center line of the slit ( 15 ), or  
       two tilted plates ( 25 ,  26 ) tilted outwardly from said diaphragm ( 19 ), being centered around a center line ( 15 ) of the single slit ( 20 ) and having parallel incident and exit surfaces.  
     
     
       27. An apparatus in accordance with  claim 26 , wherein an apex ( 22 ) of said biprism ( 24 ) points away from said slit ( 20 ).